The present invention relates to shelving and shelving systems. Generally, current shelving is fixed in the sense that one cannot expand the size or usable area of a given shelf nor change appearance or shape of a shelf without replacing the shelf altogether. In the past, extensions of various shapes and configurations have been added to shelves, but they were generally bolted to the shelf requiring additional hardware and tools to install the extension. While the need for a simple to install shelf extension could exist in almost any shelving application, there is particular need for quick and low cost options in retail settings for expanding shelves and/or changing the shape of shelves.